Motor vehicle transmissions are generally equipped with a damping device allowing vibrations to be filtered out upstream from the gearbox, so as to avoid shocks, noise, or acoustic impacts that are particularly undesirable. Damping devices of this kind are installed in particular in dual mass flywheels (DMFs) and/or friction clutches in the case of a manual or automated transmission, or in lock-up clutches that are installed in hydraulic coupling devices, in the case of an automatic transmission.
The damping devices have elastic damping means that rotationally couple a torque input element and torque output element so as to allow transmission of a torque and damping of rotational irregularities.
The document FR3000155 discloses a damping device in which the elastic damping means are constituted by two elastic blades. The two elastic blades are mounted on one of the input and output elements of the damping device, and each interact with an associated roller mounted rotationally movably on the other of the input and output elements. The blades and the rollers are configured in such a way that for an angular deflection between the input element and output element on either side of an inactive relative angular position, the roller moves along the blade and, in so doing, exerts a flexural load on the elastic blade. In reaction, the elastic blade exerts on the roller a return force that tends to bring the input and output elements back to their inactive angular position. The flexing of the elastic blade thus allows damping of the vibrations and rotational inconsistencies between the input element and output element, while ensuring torque transmission.
The performance of a vibration damping device of this kind depends on the angular stiffness of the elastic blades: the lower the angular stiffness of the damping device, the more advantageous its performance. The elastic blades must nevertheless be sufficiently stiff to allow transmission of the maximum torque generated by the engine. In order to allow a decrease in the angular stiffness of a damping device while allowing transmission of the maximum torque generated by the engine, it is thus useful to increase the maximum relative angular deflection between the torque input and output elements. The angular deflection of a damping device as described in the document FR 3000155 remains limited, however, given the constraints associated with the physical size of the blades.
In addition, the torque transmitted between the input element and output element is absorbed by the support shafts of the rollers, which are capable of deforming.
Lastly, the curve for torque transmission as a function of angular deflection is based solely on the profile of the cam surface which is carried by the blade and along which the roller rolls. The shape of the blade is subject to numerous other design constraints, however, such as the physical size and stiffness of the blade, so that certain curves for torque transmission as a function of angular deflection cannot be implemented.
The filtering performance of a damping device as described in the aforementioned document FR3000155 is therefore not entirely satisfactory.